String Handling (Cambridge (CIE) O Level Computer Science)
Revision Note
Written by: Robert Hampton
Reviewed by: James Woodhouse
String Handling
What is string manipulation?
String manipulation is the use of programming techniques to modify, analyse or extract information from a string
Examples of string manipulation include:
Case conversion (modify)
Length (analyse)
Substrings (extract)
Case conversion
The ability to change a string from one case to another, for example, lower case to upper case
Function | Pseudocode | Python | Output |
|---|---|---|---|
Uppercase |
|
| "SARAH" |
Lowercase |
|
| "sarah" |
Length
The ability to count the number of characters in a string, for example, checking a password meets the minimum requirement of 8 characters
Pseudocode | Python | Output |
|---|---|---|
|
| 7 |
|
| "Password too short" |
Substring
The ability to extract a sequence of characters from a larger string in order to be used by another function in the program, for example, data validation or combining it with other strings
Extracting substrings is performed using 'slicing', using specific start and end to slice out the desired characters
Substring has a start position of 1 in pseudocode and 0 in Python
Pseudocode | Python | Output |
|---|---|---|
|
| "Rev" |
|
| "visi" |
Worked Example
The function Length(x) finds the length of a string x. The function substring(x,y,z) finds a substring of x starting at position y and z characters long. The first character in x is in position 1.
Write pseudocode statements to:
Store the string “Save my exams” in x
Find the length of the string and output it
Extract the word exams from the string and output it
[6]
Answer
X ← "Save my exams"
[1] for storing string in X
OUTPUT LENGTH(X)
[1] for calling the function length. [1] for using the correct parameter X
Y ← 9
Z ← 5
OUTPUT SUBSTRING(X,Y,Z)
[1] for using the substring function.
[1] for correct parameters
[1] for outputting length and substring return values
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